Skin rashes


IMPORTANT The information provided is of a general nature and should not be used as a substitute for professional advice. If you think you may suffer from an allergic or other disease that requires attention, you should discuss it with your family doctor. The content of the information articles and all illustrations on this website remains the intellectual property of Dr Raymond Mullins and cannot be reproduced without written permission.

General comments
There are many causes of rashes, and most are NOT due to allergy. While there is some overlap between the rashes seen by allergy specialists and skin specialists (dermatologists), as a rule, allergy specialists (such as myself) see people with hives/urticaria, eczema and contact dermatitis and skin “vasculitis” but not other rashes like psoriasis. Dry itchy skin is best seen by a dermatologist, does not have an allergic origin, and allergy testing is unlikely to help. Rashes lasting many weeks at a time are also unlikely to have an allergic cause. Itch in the absence of rash is also unlikely to be allergic in origin. Common cause are dry skin (which may improve with avoiding routine soap and application of moisturiser) or mild hives/urticaria (which may respond to antihistamines). Itch without rash is also not allergic in origin. Please note: given increasing length of our waiting lists and the need to prioritise young children with food allergy and cases of anaphylaxis, we no longer offer appointment for assessment of rash. See your GP to be referred to a dermatologist.

Since wait lists are often long for skin, the following is useful to do while waiting:

Take photos - sometimes this helps a diagnosis when the rash is well past. Take them to your GP or specialist as a hard printed copy or on smart phone or tablet device.

Skin biopsy - “if in doubt, chop it out”. If the diagnosis is not clear, your GP can take a small sample of skin (biopsy) and send it to a pathologist for examination. Sometimes this will give an answer.

Take notes and try to answer the following questions - what makes the rash better or worse? when did it start and spread to? how did it last in ONE place before moving around? and what was the total duration? Do antihistamines help a lot, or just a bit and if they do, how quickly do they take to help? Were you on any new medicines or herbal remedies in the weeks leading up to the onset of itch/rash? Have you had this before? Are sun, heat or cold or scratching causing it? Do you have contact rashes from cosmetics, garden plants, suscreen, metal or rubber additives or perfume?

Empirical treatment

You can try antihistamines and see if there is any significant benefit.

If your skin is a bit dry, try switching to soap free washes like QV, Ego, Dermoveen, Cetaphil etc plus use a moisturiser 2/day.  Get these products from your chemist rather than supermarket. And avoid products containing food like nut oils or goats milk; that is a great way to develop allergy to these foods and I have seen many cases.

Try having loose cotton clothes next to the skin; tight clothes and wool often irritates.

You can try anti-itch cream like Zostrix or menthol containing moisturizer made up by your local compounding chemist

Last reviewed 10 April 2023